1. Field of the Invention
The present invention relates to a semiconductor laser diode module used in the field of optical communications.
2. Discussion of the Background
With the explosive growth of the Internet and other communications needs, there has developed a commensurate need for transmission systems to handle the ever increasing demand for capacity to transmit signals. Fiber optic systems have become the technology of choice for meeting this demand. Significant attention has been directed to systems which use dense wavelength division multiplexing (DWDM) to increase the number of signal channels that can be transmitted through a single optical fiber.
Semiconductor laser diodes have been used as a pumping light source for optical fiber amplifiers and as a signal light source in the fiber optic systems. The semiconductor laser diode module is a device in which a laser beam from the semiconductor laser diode is optically coupled with an optical fiber.
Erbium doped fiber amplifiers require 980 nm band and 1480 nm band semiconductor laser diode modules as pumping light sources. And Raman amplifiers require 1350–1540 nm band semiconductor laser diode modules as pumping light sources. 1550 nm band semiconductor laser diode modules are well-known as the signal light source.
Optical coupling system between the laser diode and the optical fiber is selected depending on a laser diode chip structure, the shape of the mode-field of the light emitted from laser diode, and so on, to get higher optical coupling efficiency thereby.
The semiconductor laser diode module is required to have a certain quality of optical characteristics even at a higher ambient temperature. The optical characteristics are represented by the stability of the optical coupling efficiency between laser diode and the optical fiber, the stability of the output power from laser diode, and the monitor current.